Treatment of hydrocarbon distillates with isocyanates



United States Patent ice TREATMENT OF HYDROCARBON DISTILLATES WITH ISOCYANATES Joseph A. Chenicek, Bensenville, llL, assignor to Universal .Oil Products Company, Des Plaines, 111., a corporation of Delaware No Drawing. Application February 3, 1954,

Serial No. 408,019

6 Claims. (Cl. 196-24) This invention relates to the treatment of hydrocarbon distillates and more particularly to a novel method of effecting sweetening of sour hydrocarbon distillates.

One method of removing mercaptans from a hydrocarbon distillate comprises treating the hydrocarbon distillate with an alkali metal hydroxide solution and particularly sodium hydroxidesolution, potassium hydroxide solution, etc. A modification of this process includes the use of a solutizer along with the alkali metal hydroxide solution. These and other methods are satisfactory for removing a major proportion of the mercapt'ans from the hydrocarbon distillate. However, the hydrocarbon distillate still contains mercaptans and is not sweet to the doctor test. A recent process effects the final sweetening of the distillate by incorporating therein a phenylene diamine compound.

In accordance with the present invention, the final sweetening of the hydrocarbon distillate is effected by incorporating therein a compound of different chemical structure and by means of a different chemical mechanism than heretofore utilized for this purpose.

In. one embodiment the present invention relates to a method of treating a sour hydrocarbon distillate which comprises incorporating therein an isocyanate compound.

In a specific embodiment the present invention relates to a process for sweetening sour cracked gasoline which comprises incorporating therein phenyl isocyanate.

Any suitable isocyanate may be utilized in accordance with the presentinvention. A preferred isocyanate comprises an organic isocyanate as illustrated by the following general formula:

where R comprises a hydrocarbon group including alkyl, aralkyl, alkenyl, aryl alkaryl, cycloalkyl, etc.

Illustrative compounds in which R comprises an alkyl group include methyl isocyanate, ethyl isocyanate, propyl isocyanate, butyl isocyanate, amyl isocyanate, hexyl isocyanate, heptyl isocyanate, octyl isocyanate, nonyl isocyanate, decyl isocyanate, undecyl isocyanate, dodecyl isocyanate, etc. Illustrative compounds in which R comprises an aralkyl group include benzyl isocyanate, phenylethyl isocyanate, phenylpropyl isocyanate, phenylbutyl isocyanate, phenylamyl isocyanate, phenylhexyl isocyanate, etc., naphthylmethyl isocyanate, naphthylethyl isocyanate, naphthylpropyl isocyanate, naphthylbutyl isocyanate, etc., anthrylmethyl isocyanate, anthrylethyl isocyanate, anthrylpropyl isocyanate, anthrylbutyl isocyanate, etc. It is understood that the aryl ring or rings of the phenylalkyl, naphthylalkyl and anthrylalkyl compounds may contain hydrocarbon substituents and particularly alkyl, alkenyl, aralkyl and cycloalkyl groups attached thereto.

Illustrative compoundsin which R includes an alkenyl group comprise vinyl isocyanate, propenyl isocyanate, butenyl isocyanate, pentenyl isocyanate, hexenyl isocyanate, etc., phenylethenyl isocyanate, phenylpropenyl iso- 2,723,944 Patented Nov. 15, 1955 phenyl isocyanate, amylphenyl isocyanate, hexylphenyl isocyanate, etc., similarly substituted alkylnaphthyl isocyanates and alkylanthryl isocyanates. Here again, it is understood that the specific compounds hereinbefore set forth are representative of typical compounds and other compounds include those having additional or other substituents attached to one or more of the rings.

Compounds in which R includes a cycloalkyl group preferably comprise a cyclohexyl isocyanate including cyclohexyl isocyanate, methylcyclohexyl'isocyanate, dimethylcyclohexyl isocyanate, trimethyl-cyclohexyl isocyanate, tetramethyl-cyclohexyl isocyanate, ethylcyclohexyl isocyanate, diethyl-cyclohexyl isocyanate, propylcyclohexyl isocyanate, dipropyl-cyclohexyl isocyanate, butyl-cyclohexyl isocyanate, dibutyl-cyclohexyl isocyanate, amylcyclohexyl isocyanate, hexylcyclohexyl isocyanate, etc. Other compounds in which R comprises a cycloalkyl group include those having a cyclobutyl or cyclopentyl ring. It is understood that the cycloalkyl ring may contain alkyl or other hydrocarbon substituents attached thereto.

In another embodiment of the invention the isocyanate compound may comprise a polyisocyanate. Any suitable polyisocyanate may be employed. Preferred polyisocyanates may be illustrated by the following general formula:

O=(hN-X-N=C=O where X is a hydrocarbon group to which the groups are attached to different carbon atoms. Illusnate, propylene diisocyanate, butylene diisocyanate, amylene diisocyanate, hexylene diisocyanate, etc., phenylene diisocyanate, tolylene dissocyanate, xylylene diisocyanate, etc. It is understood that triisocyanates and tetraisocyanates may be employed. In all of these compounds the -N=%O groups are attached to difierent carbon atoms.

In still another embodiment of the invention, an isothiocyanate may be employed. Any suitable isothiocyanate may be utilized, the preferred isothiocyanates having the structure of the isocyanates or polyisocyanates hereinbefore set forth except that the isothiocyanate contains sulfur instead of oxygen. Illustrative compounds include alkyl isothiocyanates as, for example, methyl isothiocyanate, ethyl isothiocyanate, propyl isothiocyanate, butyl isothiocyanate, amyl isothiocyanate, hexyl isothiocyanate, etc., aralkyl isothiocyanates as, for example, benzyl isothiocyanate, phenylethyl isothiocyanate, phenylpropyl isothiocyanate, etc., naphthylmethyl isothiocyanate, naphthylethyl isothiocyanate, naphthylpropyl isothiocyanate, etc., anthryhnethyl isothiocyanate, anthrylethyl isothiocyanate, anthrylpropyl isothiocyanate, etc.; alkenyl isothiocyanates as, for example, ethenyl isothiocyanate, propenyl isothiocyanate, butenyl isothiocyanate, pentenyl isothiocyanate, etc., phenylethe-nyl isothiocyanate, phenylpropenyl isothiocyanate, etc., naphthylethenyl isothiocyanate, naphthylpropenyl isothiocyanate, etc., anthrylethenyl isothiocyanate, anthrylpropenyl isothiocyanate, etc.; aryl isothiocyanates as, for example phenyl isothiocyanate, tolyl isothiocyanate, xylyl isothiocyanate,

ethylphenyl' isothiocyanate, propylphenyl isothiocyanate, etc.; and cycloalkyl'isothiocyanates as, for example, cyclohexyl isothiocyanate, methylcyclohexyl isothiocyanate, ethylcyclohexyl isothiocyanate, propylcyclohexyl isothiocyanate, etc. j

It will be noted that a large number of isocyanates and isothiocyanates may be employed. in accordance with the present invention. However, it isunderstood that all of these compounds are not necessarily equivalent and also that the compounds may contain certain substituted hydrocarbon groups. The substituted hydrocarbon group should not contain substituents which will react with the isocyanate group and thus the compounds should not contain substituents having a hydroxyl, mercapto, amino or similar groups but may contain, for example, ether groups, ester groups, etc.

As hereinbefore set forth the isocyanate and isothiocyanate compounds react with the mercaptans in the sour hydrocarbon distillate. to effect sweetening of the distillate. It is believed that the reaction proceeds as illustrated in the following equations, although it is not intended that applicant is to be limited to this explanation.

In the above equations, R represents a hydrocarbon or substituted hydrocarbon group corresponding to the mercaptan or mercapto' compound present in the hydrocarbon distillate. I p I Another advantage to the use of the isocyanate compounds of the present invention is that the isocyanate compound also will react with the phenols in the hydrocarbon distillate. In some cases the presence of phenols or an excess of phenols is undesirable and, in such cases, a corresponding excess of isocyanate compound is employed to thereby convert the phenols by reacting with the isocyanate compound. e

The sweetening of the hydrocarbon distillate may be effected in any suitable manner. In one embodiment, the

sweetening is effected in the presence of an alkali metal hydroxide; When the hydrocarbon distillate is first treated with an alkali metal hydroxide to remove-a major proportion of the mercaptan, the treated hydrocarbon distillate will contain a small amount of entrained alkali metal hydroxide. In many cases this small amount of alkali metal hydroxide is sufiicient for the purpose and the sweetening with the-isocyanate compound is effected in the presence thereof. In another method, it may be desirable to add alkali metal hydroxide to the hydrocarbon distillate before or after the addition of the isocyanate compound. 7

In effecting the sweetening with :the isocyanate compound, it generally is preferred to obtain intimate mixing of the isocyanate compound with the hydrocarbon distillate. In one method, the isocyanate .compound is commingled with the hydrocarbon distillate and the resultant mixture is passed through suitable mixing devices such as durion mixers, orifice mixers, etc. The resultant mixture then is introduced. into a storage tank which, when desired, may contain suitable stirring means such as mixing addles, etc. to-effect furthermixing. The sweeten.- ing is readily effected at atmospheric temperature, although elevated temperatures up to 220 F; or more may' be utilized when desired. Theamount (sf-isocyanate to-be employed will depend upon the mercaptan content of the hydrocarbon distillate and, when phenols are to be converted, upon the amount of phenols. At least one molecular proportion of isocyanate compound per molecular proportion of mercaptan and, when desired, phenol should be employed. Usually it is desirable to employ at least a slight excess of isocyanate compound in order I to insure complete reaction and thus may range up to 20 or more molecular proportions of isocyanate compound per molecular proportion of mercaptan and/ or phenol.

The process of the present invention may be used to effect sweetening of any sour hydrocarbon distillate and is particularly applicable to the treatment of gasoline and more particularly cracked gasoline. However, it may be utilized for the treatment of straight run gasolines, mixtures of cracked and straight run gasolines, cracked and/or straight run higher boiling distillates including kerosene, diesel oil, fuel oil, gas oil, etc.

It is understood that the isocyanate: compound maybe used along wi h o h r dditives in rp r ed in hydrocarbon distillates. In some cases it may be desirable to utilize the isocyanate compound along with certain phenylene. diaminecompounds as, for example, N, N'-disec.-

. further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

Example I The. gasoline used in this example was a thermally cracked gasoline having an original mercaptan sulfur con tent of 0.005% by weight, which was increased to 0.03% by the addition ofn-hexylmercaptan. Phenyl isocyanate was added to a sample of the gasoline in a molar ratio of 10:1 to mercaptan. After suitable mixing and a residence time of 24 hours at 68 F., the mercaptan content of the gasoline was decreased 97%.

Example 11 I Sweetening with phenyl isocyanate was effected in the same manner as described in Example I except that a temperature of 212 F. was employed. When using the higher temperature, the mercaptan content of the gasoline was reduced 99% after 20 minutes.

Example III In this examplethe sweetening as described in Example I was effected in the presence of sodium hydroxide. The molar ratio of phenyl isocyanate to mercaptan was 2:1. After 24 hours, the mercaptan contentv of the gasoline was reduced 97%.

Example IV The isocyanate compound in this example was urtolylene diisocyanate. When utilized in a molar ratio of 10:1 to mercaptan, 94% decrease of mercaptan sulfur was effected at 68 F. within 24 hours.

Example V When utilizing m-tolylene diisocyanate at a temperature of 212 F. and a molar ratio of 10: 1 to mercaptan, any 89% decrease in mercaptan sulfur was effected within 20 minutes.

Example VII This example may be considered as a blank or con trol run for Examples I, III, I! and V. In this example, a sample of the gasoline was maintained at 68 F. for 24 hours without the addition of an isocyanate compound. After 24 hours, there was no change in the mercaptan content of the gasoline.

Example VIII Cracked gasoline containing mercaptans may be stabilized by incorporating therein ethyl isocyanate and allowing the mixture to stand at a temperature of about 100 F.

Example IX The isocyanate compound in this example comprises phenyl isothiocyanate. This compound may be incorporated in sour cracked kerosene and will serve to etfect reduction of mercaptans.

I claim as my invention:

1. A method of sweetening a hydrocarbon distillate containing mercaptans which comprises incorporating therein an isocyanate compound and reacting the latter with the mercaptans.

2. A method of reducing the mercaptan content of a sour hydrocarbon distillate containing mercaptans which comprises incorporating therein an alkyl isocyanate and reacting the latter with the mercaptans.

3. A method of reducing the mercaptan content of a sour hydrocarbon distillate containing mercaptans which comprises incorporating therein an aryl isocyanate and reacting the latter with the merceptans.

4. A method of reducing the mercaptan content of a sour hydrocarbon distillate containing mercaptans which comprises incorporating therein an isothiocyanate and reacting the latter with the mercaptans.

5. A method of sweetening sour gasoline containing mercaptans which comprises incorporating therein an isocyanate compound and reacting the latter with the mercaptans.

6. A method of sweetening sour cracked gasoline containing mercaptans which comprises incorporating therein phenyl isocyanate and reacting the latter with the mercaptans.

References Cited in the file of this patent UNITED STATES PATENTS 664,677 Pippig et a1 Dec. 25, 1900 2,133,691 Francis Oct. 18, 1938 2,150,400 Rosen Mar. 14, 1939 2,168,674 Loane et a1. Aug. 8, 1939 OTHER REFERENCES Kalichevsky: Chem. Refining of Petroleum, 2d ed., page 267 (1942). 

1. A METHOD OF SWEETENING A HYDROCARBON DISTILLATE CONTAINING MERCAPTANS WHICH COMPRISES INCORPORATING THEREIN AN ISOCYANATE COMPOUND AND REACTING THE LATTER WITH THE MERCAPTANS. 